Alkylated phenols are useful as antioxidants in a broad range of organic materials. in the past they have been prepared by various means such as the reaction of an appropriate phenol with an olefin or an alkyl halide in the presence of an acid or metal halide Friedel-Crafts catalyst.
In a series of Russian articles (I. S. Belostotskaya and V. V. Ershov, Bulletin of the Academy of Science, U.S.S.R. 765 1964 and Ibid at 1274, 1965) a tedious nine-step method is outlined for the preparation of 4-(4-hydroxy-3,5-di-tert-butylphenyl)butanol.
According to another method phenols are alkylated with olefins selectively in an ortho position using an aluminum phenoxide catalyst, U.S. Pat. No. 2,831,989. Phenols have also been alkylated by aldehydes in an alcohol solvent in the presence of a strong base. In addition, it has been shown that phenols can be alkylated by the reaction with a primary or secondary alkanol containing 2 or more carbon atoms in the presence of an alkali metal hydroxide at elevated temperatures and pressures.
U.S. Pat. No. 3,900,410 teaches that 2,6-di-tert-butyl-4-n-decylphenol can be synthesized by reacting 2,6-di-tert-butylphenol with n-decanol in the presence of KOH and a catalyst such as cupric oxide.
U.S. Pat. No. 3,919,333 teaches that 2,6-di-tert-butyl-4-n-decylphenol can be synthesized by reacting 2,6-di-tert-butylphenol with n-decanol in the presence of KOH but without the use of cupric oxide as a catalyst.
The products derived from the process of the present invention are not alkyl phenols but the more valuable and more difficult to obtain .omega.-hydroxy alkylated phenols. The terminal p-alkylhydroxy function imparts a much lower volatility to the phenol derivative than would the corresponding p-alkyl group. This is known to be an important factor in the retention of an antioxidant at elevated temperatures. Furthermore, the alkylhydroxy group offers a convenient functional handle to those skilled in organic synthesis for conversion to a wide variety of other potentially valuable compounds, e.g. esters, acids, etc.